Rear evaporator core freeze protection method

Abstract

One embodiment relates to a method for preventing evaporator core freezing in an air conditioning system, comprising determining the occurrence of an evaporator core freezing condition for a first one of a plurality of evaporators. Determining the occurrence of an evaporator core freezing condition may be done without measuring the air out temperature first evaporator. The method also comprises adjusting an operating parameter of the air conditioning system to eliminate the core freezing condition.

1 . A method for preventing evaporator core freezing in an air conditioning system having a first evaporator core and a second evaporator core, the method comprising:
 determining an occurrence of an evaporator core freezing condition for the second evaporator cores in the air conditioning system without measuring the air out temperature for the second evaporator core; and   adjusting an operating parameter of the air conditioning system to eliminate the core freezing condition.   
   
   
       2 . The method of  claim 1 , wherein determining the occurrence of an evaporator core freezing condition comprises detecting a plurality of operating conditions and calculating a predicted value corresponding to the core freezing condition. 
   
   
       3 . The method of  claim 2 , wherein detecting comprises detecting an air out temperature for the first evaporator, a vehicle interior air temperature, and an outside air temperature. 
   
   
       4 . The method of  claim 3 , further comprising determining a voltage for a first blower motor coupled to the first evaporator, and a voltage for a second blower motor coupled to the second evaporator. 
   
   
       5 . The method of  claim 3 , wherein determining the occurrence of an evaporator core freezing condition further comprises calculating a value that correlates to the presence and/or absence of the freezing condition. 
   
   
       6 . The method of  claim 5 , wherein the value is calculated from an air out temperature for the first evaporator, a vehicle interior air temperature, and an outside air temperature. 
   
   
       7 . The method of  claim 6 , wherein the calculated value is an air out temperature for the second evaporator. 
   
   
       8 . The method of  claim 7 , wherein the air out temperature for the second evaporator is calculated according to the formula:
     T   S   =X+A T   C   +B T   O   +C V   F   +D V   R   +E T   F      
     where:
 T C  is the vehicle interior air temperature; 
 T 0  is the outside air temperature; 
 V F  is the first blower motor voltage; 
 V S  is the second blower motor voltage; 
 T F  is the air out temperature for the first evaporator; and 
 A, B, C, D, and E are all constants. 
 
   
   
       9 . A method for preventing evaporator core freezing in a vehicle air conditioning system having a plurality of evaporators, the method comprising:
 detecting an operating condition for a first evaporator;   detecting an environmental condition for the vehicle interior;   determining an occurrence of an evaporator core freezing condition for a second evaporator without measuring the air out temperature for the second evaporator; and   adjusting an operating parameter for the second evaporator, to eliminate the core freezing condition.   
   
   
       10 . The method of  claim 9 , wherein detecting an operating condition for a first evaporator comprises detecting an air out temperature for the first evaporator. 
   
   
       11 . The method of  claim 10 , further comprising determining a voltage for a first blower motor coupled to the first evaporator, a voltage for a second blower motor coupled to the second evaporator, detecting a vehicle interior temperature, and detecting a temperature outside the vehicle. 
   
   
       12 . The method of  claim 9 , wherein determining the occurrence of an evaporator core freezing condition comprises calculating an air out temperature for the second evaporator. 
   
   
       13 . The method of  claim 12 , wherein calculating comprises using a linear equation to predict an air out temperature for the second evaporator from the operating condition for the first evaporator, and the environmental condition for the vehicle interior. 
   
   
       14 . The method of  claim 12 , wherein the value is calculated from the air out temperature for a first evaporator, the vehicle interior air temperature, and the outside air temperature. 
   
   
       15 . The method of  claim 9 , wherein adjusting an operating parameter for the second evaporator comprises increasing a blower motor voltage for a blower motor coupled to the second evaporator. 
   
   
       16 . The method of  claim 9 , wherein adjusting an operating parameter for the second evaporator comprises disengaging a compressor that is in fluid communication with the second evaporator. 
   
   
       17 . An air conditioning system for a vehicle, comprising:
 a first evaporator core;   a second evaporator core;   a temperature sensor for detecting the air out temperature for the first evaporator core;   a processor configured to determine occurrence of a freezing condition for the second evaporator core without an air out temperature measurement for the second evaporator core; and   a controller having controller logic configured to adjust an operating parameter of the air conditioning system to eliminate the freezing condition for the second evaporator core.   
   
   
       18 . The air conditioning system of  claim 17 , further comprising a first blower motor coupled to the first evaporator core, and a second blower motor coupled to the second evaporator core. 
   
   
       19 . The air conditioning system of  claim 18 , wherein the controller logic is configured such that the controller increases a voltage to the second blower motor when the processor determines the occurrence of a freezing condition for the second evaporator. 
   
   
       20 . The air conditioning system of  claim 18 , wherein the processor is configured to calculate the air out temperature for the second evaporator. 
   
   
       21 . The air conditioning system of  claim 20 , wherein the air out temperature for the second evaporator is calculated from the air out temperature of the first evaporator, a vehicle interior air temperature, and an outside air temperature, using a linear equation.